Why was one seat abolished?

Perth's big population growth between the 2011 and 2015 boundary changes meant the city needed a new Lower House seat, with the WA Electoral Commission (WAEC) identifying the fast-growing area of Baldivis.

Wagin has been renamed for the same geographical reason, but its new name of Roe is a nod to its history. There have been two previous electorates called Roe, recognising the achievements of colonial explorer Sir John Septimus Roe.

What do the changes mean for the parties?

They made Labor's fight to win the 30 seats to form government harder.

Labor was the biggest net loser of the redistribution, seeing two of its seats (Collie-Preston, held by Mick Murray, and West Swan, held by Rita Saffioti) becoming nominally Liberal, although it gained Baldivis.

While the Liberals lost Eyre, they also made a net gain of one seat by taking the two Labor seats.

There was no net change to the number of seats held by the WA Nationals.

How about for the politicians?

Voting patterns at the last WA election suggest that many MPs will have a much tougher fight as a result of the redistribution.

Of course, there are many unknown factors which will affect votes at the election, from the calibre of candidates to the size of the swing against the State Government to the influence of One Nation and micro parties.